1. Field of the Invention
The present invention relates to apparatus for holding a disc-like photographic film unit while selected image frames of the photographic film unit are rotationally indexed to a predetermined position. In particular, the present invention relates to such an apparatus for positioning disc-like film units in a photographic printer.
2. Description of the Prior Art
Apparatus for holding and indexing conventional strip film on a photographic printer so that selected image frames are positioned at a print gate for transfer of the image to photographic print paper are well known in the art. However, this type of apparatus is wholly unsuited for positioning selected image frames of a disc-like film unit at a print gate wherein the individual image frames are located circumferentially about a central hub. Examples of a disc film unit are disclosed in the following U.S. patents:
______________________________________ Inventor U.S. Pat. No. ______________________________________ Sethi 4,194,822 Morse 4,208,116 Harvey et al 4,208,117 Sethi et al 4,212,673 Harvey et al 4,255,034 Harvey 4,264,169 Harvey et al 4,268,145 ______________________________________
A print gate indexing device for a disc-like film unit is disclosed in Research Disclosure of August, 1978, Disclosure No. 17287. Using the print gate indexing device, each image frame is manually advanced into the print gate. The disc-like film unit is held in a single horizontal plane while selected image frames are rotationally indexed to the print gate. However, the selected individual image frames are not necessarily optically centered or in proper focal range due to tolerance differences that may occur from individual disc-like film unit to film unit. These tolerances may be found in the hub or film containing the image frames, such as the thickness, or in the center hole and keyway in the hub which engage a center post and key that hold the film unit in a fixed angular position with respect to the indexing device.
A rotational positioning device is also disclosed in Research Disclosure of August, 1978, Disclosure No. 17289. The rotational positioning device includes an assembly from which a central shaft extends upwardly for coaxially centering the disc-like film unit on the assembly. A pair of pins also extend upwardly from the assembly for extending through cooperating apertures in the hub of the disc film unit. However, the disc film unit is not held in a manner so that a selected image frame is ensured of optical centering and proper focusing.
The Clifton et al U.S. Pat. No. 4,203,664 and the Modney et al U.S. Pat. No. 4,204,733 show film positioning apparatus which provide support and positioning of a disc-like film unit. Again, the apparatus that rotationally indexes the disc film unit for positioning images for printing in a printing gate aperture does not ensure that the particular image is optically centered or in exact focus.